The present invention relates to three-dimensional cameras and, more particularly, to systems for accurately determining the distance to various objects and portions of objects in the scene.
Various techniques are known for creating a three-dimensional image of a scene, i.e., a two-dimensional image which, in addition to indicating the lateral extent of objects in the scene, further indicates the relative or absolute distance of the objects, or portions thereof, from some reference point, such as the location of the camera.
At least three basic techniques are commonly used to create such images. In one technique, a laser or similar source of radiation is used to send a pulse to a particular point in the scene. The reflected pulse is detected and the time of flight of the pulse, divided by two, is used to estimate the distance of the point. To obtain the distance of various points in the scene, the source is made to scan the scene, sending a series of pulses to successive points of the scene.
In a similar technique, a phase shift, rather than time of flight, is measured and used to estimate distances. Here, too, the entire scene or relevant portions thereof must be scanned one point at a time.
In a third technique, which also involves scanning, at least a single radiation source and corresponding detector are used, with suitable optics which act on the light in a manner which depends on the distance to the object being examined, to determine the distance to a particular point in the scene using a triangulation technique.
The major disadvantage of all three of the above-described techniques is that each requires point by point scanning to determine the distance of the various objects in the scene. Such a scanning significantly increases the frame time of the system, requires expensive scanning equipment and necessitates the use of fast and powerful computational means.
There is thus a widely recognized need for, and it would be highly advantageous to have, a method and system for rapidly and easily determining the distance of various points in a scene without the need for scanning and complex computational capabilities.